1. Field of the Invention
The present invention relates to impellers and sewage treatment pumps including the same.
2. Description of the Prior Art
As impellers of sewage treatment pumps, impellers of vortex type, non-clogging type and screw type have been used dominantly. Additionally, an impeller in which a spiral channel is formed inside has been known (see Japanese Patent Publication No. 28-5840B).
In pumps for treating sewage with which foreign matter such as contaminants is mixed, involvement of such foreign matter and choking inside the impellers are liable to be caused, especially in low flow rate regions.